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1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"2 "http://www.w3.org/TR/html4/strict.dtd">3<!-- Material used from: HTML 4.01 specs: http://www.w3.org/TR/html401/ -->4<html>5<head>6 <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">7 <title>"libc++abi" C++ Standard Library Support</title>8 <link type="text/css" rel="stylesheet" href="menu.css">9 <link type="text/css" rel="stylesheet" href="content.css">10</head>11 12<body>13<div id="menu">14 <div>15 <a href="https://llvm.org/">LLVM Home</a>16 </div>17 18 <div class="submenu">19 <label>libc++abi Info</label>20 <a href="/index.html">About</a>21 </div>22 23 <div class="submenu">24 <label>Quick Links</label>25 <a href="https://libcxx.llvm.org/">libc++</a>26 <a href="https://discourse.llvm.org/c/runtimes/libcxx/10">Discourse Forums</a>27 <a href="https://lists.llvm.org/mailman/listinfo/libcxx-commits">libcxx-commits</a>28 <a href="https://bugs.llvm.org/">Bug Reports</a>29 <a href="https://github.com/llvm/llvm-project/tree/main/libcxxabi/">Browse Sources</a>30 </div>31</div>32 33<div id="content">34 <!--*********************************************************************-->35 <h1>"libc++abi" C++ Standard Library Support</h1>36 <!--*********************************************************************-->37 38 <p>libc++abi is a new implementation of low level support for a standard39 C++ library.</p>40 41 <p>All of the code in libc++abi is <a42 href="https://llvm.org/docs/DeveloperPolicy.html#copyright-license-and-patents">dual licensed</a>43 under the MIT license and the UIUC License (a BSD-like license).</p>44 45 <!--=====================================================================-->46 <h2 id="goals">Features and Goals</h2>47 <!--=====================================================================-->48 49 <ul>50 <li>Correctness as defined by the C++11 standard.</li>51 <li>Provide a portable sublayer to ease the porting of <a href="https://libcxx.llvm.org/">libc++</a></li>52 <li>On Mac OS X, be ABI compatible with the existing low-level support.</li>53 </ul>54 55 <!--=====================================================================-->56 <h2 id="requirements">Platform Support</h2>57 <!--=====================================================================-->58 59 <p>libc++abi is known to work on the following platforms, using clang.</p>60 61 <ul>62 <li>Darwin</li>63 </ul>64 65 <!--=====================================================================-->66 <h2 id="dir-structure">Current Status</h2>67 <!--=====================================================================-->68 69 <p>libc++abi is complete. <a href="spec.html">Here</a> is a70 list of functionality.</p>71 72 <!--=====================================================================-->73 <h2>Get it and get involved!</h2>74 <!--=====================================================================-->75 76 <p>For building libc++abi, please see the libc++ documentation on77 <a href="https://libcxx.llvm.org/BuildingLibcxx.html">building the runtimes</a>.78 </p>79 80 <p>For getting involved with libc++abi, please see the libc++ documentation on81 <a href="https://libcxx.llvm.org/Contributing.html">getting involved</a>.82 </p>83 84 <!--=====================================================================-->85 <h2>Frequently asked questions</h2>86 <!--=====================================================================-->87 88 <p>Q: Why are the destructors for the standard exception classes defined in libc++abi?89 They're just empty, can't they be defined inline?</p>90 <p>A: The destructors for them live in libc++abi because they are "key" functions.91 The Itanium ABI describes a "key" function as the first virtual declared.92 And wherever the key function is defined, that is where the <code>type_info</code> gets defined.93 And in libc++ types are the same type if and only if they have the same <code>type_info</code>94 (as in there must be only one type info per type in the entire application).95 And on OS X, libstdc++ and libc++ share these exception types.96 So to be able to throw in one dylib and catch in another (a <code>std::exception</code> for example),97 there must be only one <code>std::exception type_info</code> in the entire app.98 That typeinfo gets laid down beside <code>~exception()</code> in libc++abi (for both libstdc++ and libc++).</p>99 <p>--Howard Hinnant</p>100 101</div>102</body>103</html>104